JP-B2-4161356 describes a valve timing controller for an internal combustion engine, and the valve timing controller controls valve timing of an intake valve using pressure of hydraulic fluid. Generally, such a valve timing controller is equipped with a housing rotor interlocked with a crankshaft and a vane rotor interlocked with a camshaft. A rotation phase between the housing rotor and the vane rotor changes when the vane rotor receives the pressure of hydraulic fluid in the housing rotor. The valve timing is controlled by the change in the rotation phase.
In JP-B2-4161356, a rotation phase advanced rather than the most retard phase is defined as an intermediate phase, and the rotation phase is locked at the intermediate phase at the startup time of the internal combustion engine. In this case, the close timing of the intake valve can be made early, therefore the actual compression ratio in the cylinder becomes high. Because the temperature of gas in the cylinder is increased by heat of the compression, fuel evaporation will be promoted. Thus, the startup property of the engine can be raised at the startup time when the engine is activated from a stop condition, for example, after the engine is left under a very low temperature environment.
However, knocking may be generated by the high compression ratio in the cylinder when the engine is started under relatively-high-temperature environment, because the closing timing of the intake valve is early. Moreover, because the temperature of gas in the cylinder at the compression time becomes too much high, pre-ignition (self-ignition before ignition) may be generated at the re-startup time of the engine which is applied to a hybrid system or an idle stop system, or at the re-startup time immediately after the engine is stopped by ignition-off. Furthermore, unpleasant vibration or noise may be generated by large variation in the rotation state of the cranking shaft due to large compression work (reaction force).